Yanmar diesel smoking/ black soot

[four winds]

Originally Posted by Wotname

Well you may be correct although I doubt it. The later variant of this motor, the 3GM30 does not have "cold start" features - mechanical or otherwise; it is unlikely the earlier design was more sophisticated.

This is not a cold start feature, per se. But I just want to mention:

For cold weather starting a 3gm30, if the engine speed control is held in the high speed position the injector timing is delayed to facilitate easier starting. Of course the speed control lever must be returned immediately to a lower speed setting.

Could be a malfunction of this delaying mechanism is an issue for the OP here, but I think not.

Appears to me likely it is a problem with the individual plunger in the pump for the cylinder which responded to the decompression lever.

Edit, actually, it might be more likely the new injector happens to be faulty. Going with the odds anyway.

[a64pilot]

Originally Posted by Bronk33

How much is it to have a pump repaired? I know new, they are like $1200


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I have no idea, it's been a long time, and honestly I believe the answer is, it depends on how much damage there is, Sort of like asking how much does it cost to have my sail repaired.
If you determine it is in fact the pump, before you remove it, read up on how to time it and practice that, then I would put the engine in proper timing position whatever that is and remove the pump.
To time my old John Deere backhoe it was incredibly simple, you could only mess up by being 180 out, but not all timing is simple, I do not know how to time yours.


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[four winds]

On this engine the timing is adjusted via shims under the pump mounting surface. The plungers are driven by lobes on the camshaft...

So maybe don't misplace them and measure the thicknes just in case is best practice.

A local mechanic and friend said I could rebiuld this pump myself. I told him if it breaks I would test that theory out of necessity.

[Bronk33]

Originally Posted by four winds

On this engine the timing is adjusted via shims under the pump mounting surface. The plungers are driven by lobes on the camshaft...



So maybe don't misplace them and measure the thicknes just in case is best practice.



A local mechanic and friend said I could rebiuld this pump myself. I told him if it breaks I would test that theory out of necessity.

After in swap injectors out, I'll dig into this and update everyone.


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[sailorchic34]

Cool on progress being made. Agree that an ejector swap would be easy test. If the smoking moves to the different cylinder then its the injector. If the smoking stays on the old cylinder then odd are its that one pump that needs a rebuild. Butt I would make sure the pre-combustion chamber was fine too. Odds are its the pump

It's not rocket science to rebuild, but everything has to be spotlessly clean and care must be used that all bits and pieces are reinstalled in the right order and getting the rack alinement correct between the three pumps. That has to be exactly perfect.

[Bronk33]

Originally Posted by sailorchic34

Cool on progress being made. Agree that an ejector swap would be easy test. If the smoking moves to the different cylinder then its the injector. If the smoking stays on the old cylinder then odd are its that one pump that needs a rebuild. Butt I would make sure the pre-combustion chamber was fine too. Odds are its the pump

.

You said butt. ☺


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[sailorchic34]

LOL, Glad somebody is paying attention. Have fun with the yanmar repair

[jimbunyard]

Agreed that it may well be an injection pump issue, but I have this niggling voice in the back of my mind saying "head gasket or warped head"... arguably the more likely outcome of a severe overheat.


If you have an old injector you can make a compression gauge for a few dollars, just the cost of a 500 psi gauge and fittings, maybe a little welding.

[a64pilot]

If it were a cracked head, blown gasket, warped head etc., I'm assuming your saying the problem is from a lack of compression in the cylinder?
If that cylinder were low on compression, then de-compressing it wouldn't change things, besides it would be whitish smoke, like you get when trying to start a hard to start, cold Diesel.
But it's black smoke, which means overfueled or over loaded or both. Go to a tractor pull, about the time the get hooked up and the turbos build boost, the black smoke starts, because they are overfueling, remember back in the day, when the big trucks started pulling hills?

I'm hoping injector, haven't myself seen a pump go bad so that it overfuels one cylinder, but I'm no Professional Diesel mechanic either.


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[DeepFrz]

I'm sticking with an injector problem. May be wrong. I have been wrong once or twice before...

[jimbunyard]

Was just offering a suggestion based on the described conditions. Diesels seem to be inherently more resistant to overheat than gas, but it does happen. I've seen some funny things occur on multi cylinder engines with slight or intermittent head sealing issues, often rather counter-intuitively.


Again, it seems to be fuel related to me too, but for the engine to be overheated so much that it caused the fuel to carbonize in the injector pump it would have to get pretty damn hot. Even more so to take the temper out of governor springs.


There is also the possibility that injector pump got hot enough to coat the plungers with varnish, without carbonizing the fuel, and the problem is caused by them not having full free travel. All the internal parts of the pump must be absolutely clean and able to travel their full range of motion for it to function correctly. Fortunately, this type of pump is fairly simple and a patient, careful person can dis-assemble, clean and reassemble it without much problem.

[Bronk33]

Well I finally had my injection pump rebuilt.
I then hired a mechanic to come fix the motor...still nothing.
I'm bringing the pump back to the shop tomorrow to run on the stand and see it with my own eyes.
I've attached the work order to this for review.
Any suggestions? I will post tomorrow after I test the pump on stand.
But at this point I spent $900 to rebuild pump and 1900 for a mechanic to tell me it's still broke.


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[River Cruiser]

2 different shops did the work so far, one rebuilt injection pump and the 2nd sent out a mechanic to get running, is this correct? The problem I see arising is finger pointing between them trying to place blame on each other. The best outcome I see is if there is a problem with the rebuilt pump it should be repaired under a warranty. If the pump tests good then pulling the head is the next logical move.


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[Bronk33]

Thanks river!


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[Sardean]

As the problem started with overheating a compression test is very important to rule out or show up burnt valve, cracked head , or blown head gasket. Good luck I hope you find problem and its not too expensive

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